Christopher R. Orton

Nuclear archeology in a bottle: evidence of pre-Trinity U.S. weapons activities from a waste burial site.

During World War II, the Hanford Site in Washington became the location for U.S. plutonium production. In 2004, a bottle containing a sample of plutonium was recovered from a Hanford waste trench. Here, state-of-the-art instrumental analyses, reactor model simulations, and investigative science techniques were used to provide insights as to the origin of this unknown sample, a process collectively termed as nuclear archeology. Isotopic age dating conducted on the sample in 2007 indicated the sample was separated from the spent fuel 61.6 +/- 4.5 years earlier. The isotope (22)Na, a detectable product of a secondary nuclear reaction, proved useful as a powerful tool for nuclear forensic analysis as (1) an easily detectable signifier of the presence of alpha emitting actinides, (2) an indicator of sample splitting, and (3) a measure of the time since sample splitting. Analytical results of minor actinide isotopes and reactor model simulations confirmed the material originated from the X-10 reactor in Oak Ridge, TN. Corroborated by historical documents, we concluded this sample was part of the first batch of Pu separated at T-Plant, Hanford, the worlds first industrial-scale reprocessing facility, on December 9, 1944. This sample represents the oldest known collection of man-made (239)Pu in the world.

Measurement and analysis of gamma-rays emitted from spent nuclear fuel above 3 MeV.

The gamma-ray spectrum of spent nuclear fuel in the 3-6 MeV energy range is important for active interrogation since gamma rays emitted from nuclear decay are not expected to interfere with measurements in this energy region. There is, unfortunately, a dearth of empirical measurements from spent nuclear fuel in this region. This work is an initial attempt to partially fill this gap by presenting an analysis of gamma-ray spectra collected from a set of spent nuclear fuel sources using a high-purity germanium detector array. This multi-crystal array possesses a large collection volume, providing high energy resolution up to 16 MeV. The results of these measurements establish the continuum count-rate in the energy region between 3 and 6 MeV. Also assessed is the potential for peaks from passive emissions to interfere with peak measurements resulting from active interrogation delayed emissions. As one of the first documented empirical measurements of passive emissions from spent fuel for energies above 3 MeV, this work provides a foundation for active interrogation model validation and detector development.

FY-2010 Process Monitoring Technology Final Report

During FY 2010, work under the Spectroscopy-Based Process Monitoring task included ordering and receiving four fluid flow meters and four flow visible-near infrared spectrometer cells to be instrumented within the centrifugal contactor system at Pacific Northwest National Laboratory (PNNL). Initial demonstrations of real-time spectroscopic measurements on cold-stream simulants were conducted using plutonium (Pu)/uranium (U) (PUREX) solvent extraction process conditions. The specific test case examined the extraction of neodymium nitrate (Nd(NO3)3) from an aqueous nitric acid (HNO3) feed into a tri-n-butyl phosphate (TBP)/ n-dodecane solvent. Demonstration testing of this system included diverting a sample from the aqueous feed meanwhile monitoring the process in every phase using the on-line spectroscopic process monitoring system. The purpose of this demonstration was to test whether spectroscopic monitoring is capable of determining the mass balance of metal nitrate species involved in a cross-current solvent extraction scheme while also diverting a sample from the system. The diversion scenario involved diverting a portion of the feed from a counter-current extraction system while a continuous extraction experiment was underway. A successful test would demonstrate the ability of the process monitoring system to detect and quantify the diversion of material from the system during a real-time continuous solvent extraction experiment. The system was designed to mimic a PUREX-type extraction process with a bank of four centrifugal contactors. The aqueous feed contained Nd(NO3)3 in HNO3, and the organic phase was composed of TBP/n-dodecane. The amount of sample observed to be diverted by on-line spectroscopic process monitoring was measured to be 3 mmol (3 x 10-3 mol) Nd3+. This value was in excellent agreement with the 2.9 mmol Nd3+ value based on the known mass of sample taken (i.e., diverted) directly from the system feed solution.

MULTI-ISOPTOPE PROCESS MONITOR: A COMPARISON OF MODEL AND EXPERIMENTAL VALIDATION

The MIP Monitoring concept was demonstrated through a series of simulations as well as experiments. While qualitatively these studies generated similar results, there were significant differences between the simulated and experimentally determined spectra. This chapter investigates these differences between modeled and experimentally determined CZT gamma spectra and subsequent PCA analysis generated from each.

FY 2009 Progress: Process Monitoring Technology Demonstration at PNNL

Pacific Northwest National Laboratory (PNNL) is developing and demonstrating three technologies designed to assist in the monitoring of reprocessing facilities in near-real time. These technologies include 1) a multi-isotope process monitor (MIP), 2) a spectroscopy-based monitor that uses UV-Vis-NIR (ultraviolet-visible-near infrared) and Raman spectrometers, and 3) an electrochemically modulated separations approach (EMS). The MIP monitor uses gamma spectroscopy and pattern recognition software to identify off-normal conditions in process streams. The UV-Vis-NIR and Raman spectroscopic monitoring continuously measures chemical compositions of the process streams including actinide metal ions (uranium, plutonium, neptunium), selected fission products, and major cold flow sheet chemicals. The EMS approach provides an on-line means for separating and concentrating elements of interest out of complex matrices prior to detection via nondestructive assay by gamma spectroscopy or destructive analysis with mass spectrometry. A general overview of the technologies and ongoing demonstration results are described in this report.

FY09 PROGRESS: MULTI-ISOTOPE PROCESS (MIP) MONITOR

Model and experimental estimates of the Multi-Isotope Process Monitor performance for determining burnup after dissolution and acid concentration during solvent extraction steps during reprocessing of spent nuclear fuel are presented.